<?php

/*
 * This file is part of SwiftMailer.
 * (c) 2004-2009 Chris Corbyn
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * A MIME entity, such as an attachment.
 *
 * @package    Swift
 * @subpackage Mime
 * @author     Chris Corbyn
 */
interface Swift_Mime_MimeEntity extends Swift_Mime_CharsetObserver, Swift_Mime_EncodingObserver
{
	/** Main message document; there can only be one of these */
	const LEVEL_TOP = 16;

	/** An entity which nests with the same precedence as an attachment */
	const LEVEL_MIXED = 256;

	/** An entity which nests with the same precedence as a mime part */
	const LEVEL_ALTERNATIVE = 4096;

	/** An entity which nests with the same precedence as embedded content */
	const LEVEL_RELATED = 65536;

	/**
	 * Get the level at which this entity shall be nested in final document.
	 *
	 * The lower the value, the more outermost the entity will be nested.
	 * @see LEVEL_TOP, LEVEL_MIXED, LEVEL_RELATED, LEVEL_ALTERNATIVE
	 *
	 * @return int
	 */
	public function getNestingLevel();

	/**
	 * Get the qualified content-type of this mime entity.
	 * @return string
	 */
	public function getContentType();

	/**
	 * Returns a unique ID for this entity.
	 *
	 * For most entities this will likely be the Content-ID, though it has
	 * no explicit semantic meaning and can be considered an identifier for
	 * programming logic purposes.
	 *
	 * If a Content-ID header is present, this value SHOULD match the value of
	 * the header.
	 *
	 * @return string
	 */
	public function getId();

	/**
	 * Get all children nested inside this entity.
	 *
	 * These are not just the immediate children, but all children.
	 *
	 * @return Swift_Mime_MimeEntity[]
	 */
	public function getChildren();

	/**
	 * Set all children nested inside this entity.
	 *
	 * This includes grandchildren.
	 *
	 * @param Swift_Mime_MimeEntity[] $children
	 */
	public function setChildren(array $children);

	/**
	 * Get the collection of Headers in this Mime entity.
	 *
	 * @return Swift_Mime_Header[]
	 */
	public function getHeaders();

	/**
	 * Get the body content of this entity as a string.
	 *
	 * Returns NULL if no body has been set.
	 *
	 * @return string|null
	 */
	public function getBody();

	/**
	 * Set the body content of this entity as a string.
	 *
	 * @param string $body
	 * @param string $contentType optional
	 */
	public function setBody($body, $contentType = null);

	/**
	 * Get this entire entity in its string form.
	 *
	 * @return string
	 */
	public function toString();

	/**
	 * Get this entire entity as a ByteStream.
	 *
	 * @param Swift_InputByteStream $is to write to
	 */
	public function toByteStream(Swift_InputByteStream $is);
}
